The invention concerns a procedure for control and adjustment of a clutch in a stepless, automatic transmission in which an electronic control apparatus with two regulation circuits determines the adjustment of the clutch. The invention further concerns an apparatus for the execution of the procedure for the control and adjustment of a clutch in a motor vehicle transmission.
By the term, xe2x80x9cclutchxe2x80x9d, within the concept of the invention, it is to be understood that a xe2x80x9cstart-upxe2x80x9d clutch is meant. Under this classification are to be found clutches which are positioned between an internal combustion motor and an automatic transmission, also torque converter, bypass clutches as well as such clutches and brakes in automatic transmissions which can be employed both for start-up and for shifting.
In particular, the invention concerns wet start-up clutches which can be integrated into an automatic transmission. The majority of such clutches, however, are installed as a component assembly on the input side of the transmission. However, as a start-up element for an automatic stepless transmission, especially in a CVT, these wet clutches are also placed as a component assembly on the output side of the transmission.
Normally, clutches and brakes in automatic transmissions or in automatic stepped transmissions are electro-hydraulically activated, and operate independently of intervention by the shifting elements. The said clutches and brakes then perform as a gear position shifting means, or as gear change clutches in an assembly, or start-up clutches or yet as converter bypass clutches. To enable this service, usually an electronic transmission control apparatus acts specifically for an individual vehicle, while processing transmission and driving demands which are dependent upon the driving condition. These specifics can include axle gear ratios, transmission gear ratios, motor torque, motor rotation speed, throttle pedal position, or the like. The acquired data, as input, is processed in an electronic control apparatus and, by means of actuators and hydraulic valves, then converted into hydraulic control pressures designated for corresponding clutches. This latter data input would include clutch related signals, such as pressure control for pressure regulation or pressures during a gear change, and/or speed of rotation control during slip operation, all of which are transmitted to a hydraulic control apparatus and by means of actuators and hydraulic valves care converted to hydraulic control pressures for the corresponding clutch.
A procedure for the control of a start-up clutch, along with other matters, has been made known by DE 44 09 122 A1. The start-up control comprises, in this case, two phases. In a first phase, the input speed of rotation of the clutch is directed to a set-speed of rotation, wherein this set speed of rotation is determined by the driver""s demand for power and a current mode of driving is determined. In the second phase, the difference between the input side and the output side speeds of rotation of the clutch is reduced to a set value of zero.
DE 39 37 976 discloses a procedure for the control of a clutch which serves for clutch non-interaction due to vibration disturbance. The slippage in the clutch changes, in this case, and is dependent upon speed-of-rotation-equalization as determined at the transmission output.
EP 0 214 989 B2 again makes known the use of a clutch integrated in an automatic transmission as a start-up element.
DE 198 40 573, of the applicant which up to now has not been published, describes a procedure for the control and regulation of a clutch in a stepless, automatic transmission for a motor vehicle according to which, the clutch control and regulation occurs during two driving conditions by means of a first control circuit. The degree of this control corresponds to the actual value of a difference in speed of rotation of the clutch. The first condition corresponds to a start-up process and the second condition corresponds to driving with a variable ratio arrangement.
From the likewise non-published DE 198 40 572 of the Applicant, a process for the control and regulation of a clutch in an automatic stepped transmission with traction interruption, that is to say, in an automatic stepped transmission which can shift in accord with the load is made known. With this method, during three conditions of driving (enumerated below), control is effected by means of a first regulating circuit. The degree of regulation, or-control, corresponds to the actual value of a difference in speeds of rotation of the clutch. The first condition of driving relates to a start-up process. The second condition of driving pertains to driving with a constant gear ratio. The third condition comes into play when load shifting, that is to say, a change of the ratio is initiated by a first into a second gear step of the automatic drive.
Given the above description of the state of the technology, the present invention has the purpose of making available a procedure for the control and regulation of a clutch in a stepless transmission for a motor vehicle along with an apparatus for the execution of said procedure for the control and regulation of a clutch, and to further develop the same with consideration given to the manifold usages of a single clutch, especially to achieve an improved quality of regulation and control-dynamics, in connection with an automatic stepped-transmission.
The object of the invention is to be found advantageously therein in that, during the first condition of driving, a first regulation circuit is employed for the control and regulation of the clutch. The degree of regulation corresponds to the actual value of the speed of rotation of the motor n_MOT_IST and corresponds to the input speed of rotation of the clutch. During the second condition of driving, a second regulating circuit is used, the degree of regulation being equivalent to the actual value of the difference in rotational speeds of the clutch dnK_IST. Finally, during the third condition of driving, the clutch is subjected to controlled values of pressure which, in turn, are influenced by various factors. The three conditions of driving correspond, in the above, to a first condition comprising a start-up procedure when under a threshold vehicle driving speed during a traction operation, a second condition marked by driving the vehicle at a speed above the start-up procedure, i.e., above a threshold driving speed with a positive or a negative torque during a traction or a compression mode, as well as driving under a vehicle threshold speed with negative torque at the output, and a third condition, wherein the start-up condition differentiates itself from the other driving conditions in that the driving speed is less than a threshold value and the vehicle motor can stall under this said threshold value.
By means of the procedure in accord with the invention, a better reaction of the transmission control advantageously is achieved in regard to load shifting, especially upon letting up on the fuel feed in the third condition since, in this case, the control still performs an empty action upon the pressure at the clutch although no adjustment takes place.
Further, the difference in speeds of rotation over the clutch is not brought back to a value of zero. The advantageous consequence of this is that a non-interaction vibration between the motor and the transmission is achieved.
In an advantageous development of the invention, the proposal is made that the change in gear ratio in a stepless automatic transmission is principally determined by a third regulating circuit, and that the first and third, or second and third regulating circuits are bound together by means of a non-interacting network, which exhibits a first and a second signal path, respectively. More advantageously, it is proposed here, that for the change of the ratio from a first to a second gear ratio, an individual regulating circuit is employed, namely, the third circuit.
For this case, as for the situation during the ratio-change, the two regulating circuits, which find themselves in action, are bound to one another by a non-interacting network which advantageously allows that these two said regulating circuits do not interfere with one another during their functioning.
The proposal extends itself further in that during a gear ratio change from a first to a second gear ratio, the automatic transmission, during the first condition of driving, the first regulating circuit, by means of the non-interacting network, influences the third regulating circuit by means of a first signal path and in that the third regulating circuit, by a non-interacting means of the non-interaction network via a second regulation circuit, acts on the first regulation circuit.
In the case of a ratio change from a first to a second gear ratio during the second driving condition, the second regulating circuit acts by means of the non-interacting network, by way of the first signal path, on the third regulating circuit. At the same time the third regulating circuit acts, by means of the non-interacting circuit through a second signal path on the second regulating circuit.
In a development of the invention, the proposal is made to calculate the pressure level pAK of the clutch from an offset value pAK_OFF and a cumulative value pSUM. The cumulative value PSUM is principally determined by the sum of the controlled torque MK(ST) of the clutch, the regulated summated torque MK(RE)xe2x80x2 of the clutch, and the disengaged load shift torque MLS_ENT.
The controlled torque MK(ST) is principally derived from the dynamic torque of the clutch, i.e., MDYN_K and the motor torque MMOT.
The regulated summated torque MK(RE)xe2x80x2 of the clutch is determined from the dynamic motor torque MDYN_MOT and a regulated torque MK(RE).
The regulated torque MK(RE) in the first condition of driving is principally computed from set/actual comparison of one of the motor speeds of rotation n_MOT equivalent values and a load specific signal DKI of a driver by a device for increasing or decreasing the load.
The gear-ratio-dependent set difference in speeds of rotation dn_SW(i) for a start-up gear stage of the automatic transmission is determined, in the second condition of driving, by means of a characteristic field KF(i). This characteristic curve presents an arrangement of load specific signals of the driver DKI and an output speed of rotation nAB of the clutch.
The regulated torque in the second condition of driving MK(RE) is principally drawn out of the set/actual comparison of the speeds of rotation difference dnK_SW, dnK_IST of the clutch and a load specific signal initiated by a driver by a device for increasing or decreasing the load.
Advantageously the regulator contains a limited integrator, to which is fed as input the deviation from regulation from the set/actual comparison of the rotational speeds dnK_SW, dnK_IST of the clutch, the displacement speed of the load signal DKI and the relation of the actual to set values of the difference in rotational speeds, i.e., dnK_IST/dnK_SW of the clutch.
The set value of the difference in speed of rotation of the clutch dnK_SW advantageously arises from the addition of a set-value-offset dnLS_SW and a gear ratio dependent difference in rotational speed at the clutch dn_SW(i).
Advantageously, in the case of a transition from the first or third condition of driving to the second condition of driving, the set value of the difference in rotational speeds dnK_SW is conducted through a filter, this especially being a dynamic delay member, whereby, as the starting value of the delay member is set at the actual value of the difference in speeds of rotation, namely, dnK_IST.
In the second condition, there is an increase in the set value offset of the difference in speeds of rotation, dnLS_SW of the clutch, during a gear ratio change from a first into a second gear ratio stage of the automatic transmission.
The characteristic fields are here so formulated, that, at a vehicle speed v less than a threshold value GW, an increased difference in the speeds of rotation dn_SW(i) of the clutch arises. By this action, an effective prevention of stalling during non-start-up gear positions, that is, for example, while driving at a constant ratio of the automatic transmission is achieved.
Advantageously, also in the second condition of driving, at a vehicle speed v less a threshold value GW, an increased difference in speeds of rotation dn_SW(i) of the clutch is considered to be a deterrent to stalling. When this is done, the increased difference in rotational speeds dn_SW(i) is input as larger than the difference from the most minimal speed of rotation of the internal combustion motor nMOT_MIN and the output speed of rotation nAB of the clutch.
In the third condition of driving, the pressure level pAK of the clutch arises from a pressure value, which is dependent upon one or several of the following values: throttle flap position; brake activity; brake pressure; motor torque and load shifting or the like, and wherein the pressure value is a controlled value.
More advantageously, an apparatus is made available for the execution of a procedure for the control and regulation of a clutch in a stepless automatic transmission for a motor vehicle. This apparatus provides an electronic control system with a first and a second regulating circuit, whereby the degree of regulation of the first regulating circuit is equivalent to the actual value of the motor speed of rotation and the degree of regulation of the second regulation circuit is equivalent to-the actual value of a difference in speeds of rotation at the clutch.
Furthermore, a third circuit of regulation is provided which is connected with the first and the second circuits of regulation through a non-interacting net work, and wherein the third regulating circuit determines the load shifting.
Further the non-interacting network exhibits a first and a second signal path, respectively, between the first and the third regulation circuit and also between the second and the third regulation circuit.